In various manually operated cutting tools for cutting branches or similar objects to be cut it is generally known to utilize a mechanism that allows stepwise cutting of the object to be cut. The mechanisms are arranged to work such that when an object to be cut, having a first diameter or thickness, is placed in the cutting jaw of the cutting tool the cutting is performed with one cutting movement. Whereas, when an object to be cut, having a second diameter or thickness that is larger than the first diameter or thickness, is placed in the cutting jaw of the cutting tool, the cutting of the object takes place stepwise with two or more successive cutting movements, whereby each cutting movement cuts a portion of the diameter or thickness of the object to be cut. Cutting tools of this kind generally comprise a first and a second elongated elements, which further comprise a first and a second handles, whose relative turning movement allows the cutting jaw of the cutting tool to be set in a closed and an open position. These cutting tools generally also comprise an immobile blade, e.g. an anvil, and a movable blade that moves in response to the relative movement of the first and the second handles. The first or the second of the handles is further connected operationally to a movable blade with a lever mechanism for force transmission. The first end of the lever in the lever mechanism is thus connected to the first or the second elongated element in an articulated manner at a pivot point. The movable blade is further provided with two or more engagement points wherewith the second end of the lever optionally engages in order to enable stepwise cutting as presented above. A tool of this kind is set forth in U.S. Pat. No. 5,511,314. In addition, these cutting tools, which comprise one moving blade and one immobile blade or anvil, are conventionally provided such that the anvil or the immobile blade are provided integrally or fixedly in one of the handles.
One disadvantage with the above arrangement is that in these known cutting mechanisms the lever and the engagement points are implemented such that the cutting force exerted on the blade by means of the relative movement of the handles is not transmitted to the blade in an optimal manner, but force is lost, whereby in all cutting steps there is not an equal amount of force available. In that case, in the known cutting tool's engagement points, wherewith the second end of the lever engages, are placed substantially successively away from the pivot point about which the moving blade rotates during the cutting movement. In other words, the engagement points are placed on a line extending substantially radially away from the pivot point about which the moving blade rotates. In that case, all engagement points are significantly at different distances from the pivot point about which the lever turns the moving blade, whereby a good lever position is not achieved in all engagement points, but in at least some of the engagement points the lever is in a disadvantageous position for transmitting force to the blade, whereby cutting becomes cumbersome and more force must be exerted on the handles. A further disadvantage is posed by the fact that when one of the blades or the anvil is provided fixedly in one of the handles, the cutting movement is not symmetrical for both hands, which makes cutting more difficult. In addition, in these known tools enabling stepwise cutting considerably more force is required at the beginning of each cutting movement than at the end.
It would be advantageous to provide a cutting tool such that the above-mentioned problems may be solved. It would also be advantageous to provide a cutting tool with an anvil part which comprises at its distal end an anvil or a first blade, the anvil part comprising a first pivot point, a second pivot point and a third pivot point, and a first elongated element which comprises a first handle and a first tooth gear part, the first elongated element being connected in an articulated manner to the anvil part at the second pivot point, and a second elongated element which comprises a second handle and a second tooth gear part and which is connected in an articulated manner to the anvil part at the third pivot point such that the first and the second tooth gear parts are arranged to engage with one another by means of the first and the second tooth gear parts. It would be further advantageous to provide a metal plate which comprises a second blade forming a cutting jaw with the anvil or the first blade and which metal plate is connected in an articulated manner to the anvil part or to the first blade at the first pivot point and connected operationally to the first elongated element for opening and closing the cutting jaw in response to the relative turning movement of the first elongated element and the second elongated element about the second and the third pivot point respectively.
It would also be advantageous to provide a cutting tool where the first and the second elongated elements and hence the handles are connected in an articulated manner to the anvil part or the first blade as well as to one another with tooth gear parts and the second of the elongated elements is further connected with a lever mechanism to the second blade which is connected in an articulated manner to be rotatable in relation to the first blade. It would also be advantageous to provide a cutting tool with an engagement device in the metal plate and arranged to receive the second end of a first lever optionally at two or more engagement points in relation to the first pivot point so as to perform stepwise cutting movements.
The cutting tool according to the embodiments shown and described herein provide a cutting tool having one fixed blade or anvil and one moving blade, but in spite of that the cutting movement is substantially symmetrical for both hands, because both handles are separately pivoted to the anvil part or the fixed blade. The handles are further connected to one another with tooth gear parts. In addition, the lever mechanism enables stepwise cutting of an object to be cut with the cutting tool comprising the above-mentioned features. By means of the lever mechanism the cutting force of each step of the stepwise cutting can be rendered good by optimizing the lever arm produced by the lever mechanism. In other words, the lever mechanism permits each cutting step to be good, and because highest force for cutting is generally required in the last cutting step, where the object to be cut is cut off, said lever arm will be good also in the cutting step that closes the cutting jaw completely. In addition, need for force in each cutting movement is considerably more equal throughout than in known solutions.